Medical experts have long linked stress to people overeating comfort foods or binge-type meals that are high in sugar, fat and calories when one is feeling ‘stressed out.’ That is because the stress hormone cortisol is an essential player in metabolism and helps to determine where fat is stored.

But previous studies that examined links between cortisol and obesity mostly relied on measuring the amounts of the hormone in the blood, saliva and urine, which can fluctuate based on time of day or other external situations. These studies were unable to capture and record true long term cortisol levels.

Produced in the adrenal glands, the hormone is released into the bloodstream during times of stress. Cortisol suppresses inflammation, regulates blood pressure, maintains blood supply and gives the body an energy boost to handle emergencies.

Researchers at University College London, whose findings were published in the journal Obesity, found that examining hair samples for cortisol provided a longer duration snapshot of a person’s stress levels, because of the amount of time it takes for hair to grow.

“Hair cortisol is a relatively new measure which offers a suitable and easily obtainable method for assessing chronically high levels of cortisol concentrations in weight research and may therefore aid in further advancing understanding in this area,” said Dr. Sarah Jackson (UCL Epidemiology and Public Health) who led the research.

Measuring Cortisol in Hair Samples

To obtain the data, the English Longitudinal Study of Ageing surveyed the information of 2,527 men and women over a span of four years. The study participants ranged from 54 years of age and older. Scientists took a 2 cm-long lock of hair from each participant and cut as close to each person’s scalp as possible. This sample represented nearly two months of hair growth that could be linked to amassed levels of cortisol. The study participants’ weight, body mass index and waist circumferences were examined as well as how their hair cortisol related to their obesity levels.

Those with higher levels of cortisol in their hair samples were heavier overall and had larger waist circumferences and higher body mass indexes (BMI). The participants who were classified as being obese or overweight had an extremely high level of cortisol. These were individuals with BMIs greater than or equal to thirty — men with waist circumferences more than or equal to 102 cm, and 88 cm for women.

“These results provide consistent evidence that chronic stress is associated with higher levels of obesity,” said Dr. Jackson. “People who had higher hair cortisol levels also tended to have larger waist measurements, which is important because carrying excess fat around the abdomen is a risk factor for heart disease, diabetes, and premature death.”

Study Limitations of the Data

While this new research offered a breakthrough in the measurement of long term cortisol levels in people, researchers involved say the study does have limitations. They include the fact that all participants were older and white. And while the findings establish a link between chronic high level cortisol exposure and obesity, it doesn’t exactly establish a cause and effect factor. This point is backed by Susan Fried, Director of Translational Adipose Biology and Obesity at the Diabetes Metabolism Obesity Institute.

“The obesity in the people studied likely developed many years earlier. Thus, these high hair cortisol values may simply reflect social or biological stress associated with being obese,” Fried, who is also a professor but not involved in the study, wrote to CNN in an email. “It is possible, for example, that the social stigma that people with obesity often endure may cause mental stress and hence high cortisol levels. It is also possible that stress over the past few months may also be due to medical conditions caused by obesity, for example it may be difficult and painful for people with obesity to walk.”

Dr. Jackson said that she and her researchers will continue to weigh and measure their study participants every four years to determine exactly how stress affects the body over time.

Ronke Idowu Reeves is a writer and journalist who hails from Brooklyn, NY. Her news and entertainment stories have appeared on WABC-TV-New York, Fox News Channel, VH1, BET.com plus in Sundance Film Festival’s Sundance Daily Insider and People Magazine.

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